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BIG PHYSICS, BIG QUESTIONS –

Shark virgin births seen in two generations for the first time

By Andy Coghlan

IT WASN’T a one-off. Virgin births are far more common than we thought, and can continue for multiple generations. These two surprising findings are overturning everything we knew about parthenogenesis.

Some animals, including Komodo dragons and domestic chickens, can sometimes produce offspring without copulating with a male. Females do this by using one of two methods to add an extra set of chromosomes to their eggs, producing either full- or half-clones of themselves. It had only been seen in captivity – until two virgin births were recently recorded in a wild sawfish and pit viper.

The process was also thought to be a dead end, producing infertile offspring. Now, for the first time, researchers have seen an individual born through parthenogenesis go on to have its own virgin birth.

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“The discovery implies virgin births may actually be an alternative to sexual reproduction”

The finding was made by following a captive female whitespotted bamboo shark. Genetic testing revealed her offspring had no father, and one of these then went on to have her own pups by parthenogenesis (Journal of Fish Biology, doi.org/bbsj).

The finding shows that an animal conceived by parthenogenesis can be fertile and isn’t an evolutionary dead end, says Nicolas Straube of the Bavarian State Collection for Zoology in Munich, who led the study. “It implies that parthenogenesis may be an alternative to sexual reproduction.”

A second study has found that parthenogenesis happens frequently in 20 snake species, adding evidence to the idea that virgin births aren’t just a rare trick (Biological Journal of the Linnean Society, doi.org/bbsh).

“Both papers show that parthenogenesis occurs in more vertebrates than previously thought,” says Jim Bogart of the University of Guelph in Canada.

Image credit: Dave Fleetham/Design Pics/Corbis

This article appeared in print under the headline “Shark virgin births continue for generations”